Depression has been consistently shown to be a strong, independent risk factor for recurrent acute coronary syndromes (ACS). The mechanisms through which depression mediates this excess risk, however, remain unclear. Depressed patients with co-morbid chronic medical illness are less adherent to their prescribed medications, suggesting that non-adherence to medications may, at least partly, explain the excessive recurrence rate of ACS in depressed coronary patients. The hypothesis that depressed coronary patients are less adherent to prescribed medications than non-depressed coronary patients will be tested. Specifically, using a prospective case-control design of patients admitted for ACS (N=136), daily adherence with prescribed aspirin therapy will be monitored upon discharge utilizing a medication event monitoring system (MEMS) for 16 weeks. A secondary hypothesis will explore whether depression treatment in depressed coronary patients improves adherence compared to depressed coronary patients not treated for depression. Beyond investigating the depression-ACS relation, determining whether depressed coronary patients are less adherent with medications may identify a high-risk clinical population in whom intervention may be warranted.